I was replacing the rivets on my 4 rivet mast base, when I found this underneath. I knew I should of changed those rivets last fall. 2 years ago I changed the rivets and did a crappy job, cause a few months later the mast base had worked its way up almost an 1/8 inch. That's what I get for being lazy.

I do have a spare FWD crossbar which is from an 81.

I don't think this crack is fatal, especially now since I re did the rivets perfectly. I used a clamp before doing the rivets and loosened the dolphin striker rod. I think it was caused from the mast base putting all the pressure on the fwd part of the crossbar due to the 1/8 inch play.

I would put a little alumilead(sp?) in there as well and fair it off. That will keep the step from trying to rock forward into the void and streching the rivet in the back. Forget the $6, its the time your gonna spend that will be the worst of it. New rivets are many times harder to drill out than old siezed up ones.

You probably don't want to hear this, but in my opinion, if you've got another spare crossbar in good shape that's sitting around, I'd swap them out.

Why use a part that is suspect when you've got a perfectly good one ready to go? Especially when it comes to the most heavily loaded and structrually important component on the boat. Use your best judgement, if you think it's OK to keep using this one, then maybe it is. I've had two H18 front crossbars crack at the mast step over the years, and I've always changed them out immediately (note that they were cracked vertically, not horizontally like yours). This crack doesn't look horrible, but why risk it?

Anyway, that's my two cents. If you decide to continue using this one, drill the holes at the ends of the crack and keep a careful eye on it.

Just had a thought....I wonder if there would be any benefit by bedding the mast step to the crossbar using thickened epoxy / marine tex. This might help to spread the load over the front crossbar where the contour of the mast step varies from the shape of the crossbar. It might also help prevent the mast step from wobbling around and working the rivets loose I'm not sure how long it would last though or if it would just crack out.

I think epoxy would be better. I may try this too because I've got a mast step that's a little loose fore & aft so I will probably pop it off and re-seat it. I think Marine Tex would probably be the way to go. It's like $15 for a can that is more than enough for this job.

I would lightly sand the crossbar and mast step and then wipe clean with acetone. Then put a thin layer of M-tex on each surface, put the mast step on the crossbar, install the rivets and pull them about 2/3's of the way, wipe off any excess M-tex and allow it to cure. After it's fully cured, then I'd do the final pull on the rivets.

"Marine Tex" comes in white and black .... it is also useful in filling the "hollows" in H17/18 rudder cams so they last longer .... I've even used it to repair exhaust manifolds were the "seating" surface was pitted .... filled it in/file smooth/re-install the manifold ... and it worked!!! ... much to my surprised amazement ...

I don't have experience with JB weld. I've used marine tex quite a bit and it is quite hard and strong. Again, I've never bedded the mast step before, so I don't even know if it will help. It just seems like it might tighten up the mast step and prevent the rivets from working loose.

Marine tex comes in white and grey. The grey would probably be a close match for faded black or clear anodize. But really color matching isn't a big concern since it will only be under the step.

It looks like the grey marine tex also has over 50% higher compressive strength than the white, so the grey would definitely be the way to go.